Printing machine with a roller platen releasing device

ABSTRACT

A carriage supporting a roller platen frame is manually moved in a printing stroke and in a return stroke over type wheels on a printing bed. A releasing lever, resiliently connected with the roller platen frame, shifts the same between a printing position and an inoperative position when engaged and displaced by fixed actuating blocks during the carriage movements. A biased holding lever arrests the roller platen frame in either position. The resilient connection between the releasing lever and the roller platen frame, preferably including abutting slide faces, permits movement of the yielding releasing lever over the actuating blocks after the frame has been placed in the printing position or the inoperative position.

United States Patent 1191 ()zaki et al. 1 June 4, 1974 [54] PRINTINGMACHINE WITH A ROLLER 3,410,207 11/1968 Barbour 101/269 PLATEN RELEASINGV C 3,446,144 5/1969 Frampton et a1. 101/269 3,538,848 11/1970 Barbour101/269 [75] inventors: Yoshiakl 0zak1; Fumlyuk Mls mar 3,650,209 3/1972Allport 101/269 both of Tokyo, Japan [73] Assignee: Janome SewingMachine Co., Ltd., P im y xa n -Robert E. Palfrey Tokyo, Japan Assistan!ExamineF-E. M. Coven Filed: Mar. 1972 Attorney, Agent, or F1rmM1chael S.Strlker [21] Appl. No.: 230,903 [57] ABSTRACT A carriage supporting aroller platen frame is manu- [3,0] Forelgn Apphcatmn Prmmy Data allymoved in a printing stroke and in a return stroke I Feb. 24, 1971 Japan46-11211 Over type Wheels on a printing bed A releasing leverYresiliently connected with the roller platen frame, [52] US. Cl. 101/269Shifts the same between a printing position and an [51] Illll. Cl B43/04 Operative position when engaged and displaced by [58] Fleld ofSearch 101/269-274, fixed actuating blocks during the Carriage movementsl0l/45 56 A biased holding lever arrests the roller platen frame ineither position. The resilient connection between [56] References C'tedthe releasing lever and the roller platen frame, prefer- UNITED STATESPATENTS ably including abutting slide faces, permits movement 1,305,7786/1919 Cushing et a1. 101/269 of the yielding releasing lever Over theactuating 3,018,725 1/1962 Maul et al 101/269 blocks after the frame hasbeen placed in the printing 3,260,199 7/1966 Huntley et al. 101/269position or the inoperative position. 3,274,931 9/1966 Patterson 101/2693,388,660 6/1968 Hight 101/269 9 Claims, 6 Drawing Figures 251 23 5.////l"/// //,l III/MI l0 9/ v /0 PATENTED HH 4191 3814.015

V min 3 [If 3 PRINTING MACHINE WITH A ROLLER PLATEN RELEASING DEVICE Theinvention relates to printing machines and more particularly relates toa roller platen releasing device for printing machines. In a printingmachine having a carriage mounted on the printing bed for transversemovement over type characters and a material to be imprinted such as asales slip provided on the printing bed, it is a primary object of theinvention to make the roller platen on the carriage press the copy sheetonto the type characters during transverse movement of the carriage inone direction for realising printing on the material to be printed, andthen to hold the roller platen in a position spaced up from the printingbed during return movement of the carriage in the opposite direction sothat reprinting on the printed material may be prevented. Another objectof the invention is to provide a roller platen support which isadjustable to adjust the printing pressure of the roller platen inaccordance with the thickness of the material to be printed.

In order to avoid a reprinting operation of the machine during thereturn strokeof the carriage with the roller platen, it has beenproposed that the roller platen is to be pressed against the printingbed during the movement of the carriage in one direction transversely ofthe printing bed, and that the roller platen is to be held in a positionspaced from the printing bedduring the returning movement of thecarriage in the opposite direction. But the conventional roller platenreleasing devices are not suited for precise operations.

SUMMARY OF THE INVENTION The present invention has been designed toeliminate such disadvantages of the conventional printing machines.According to the present invention, the roller platen supported on thecarriage is held arrested in two restricted positions for printing andnon-printing by means ofa spring biased holding lever. For the purposeof preventing the roller platen from reprinting the sales slip, theroller platen is turned to printing and inopera tive positions againstthe action of the holding lever by means of a releasing lever which isactuated during each cycle of transverse movements of the carriage androller platen over the printing bed.

As a roller platen support, the present invention uses an eccentricshaft which turnably supports a swingable frame which in turn rotatablysupports the roller platen, and the eccentric shaft is adjustablymounted on the carriage. According to the present invention, byadjusting the eccentricity of the eccentric shaft with respect to theswingable frame, the position of the roller platen is appropriatelyadjusted relative to the printing bed. Thus the printing pressure of theroller platen is variably changed in accordance with the material to beprinted. In this invention, such an adjustment of the rol ler platenwill be easily accomplished.

The other features and advantages of the present invention will beapparent from the following description of the preferred embodiment inreference to the attached drawings:

BRIEF DESCRIPTION OF THE DRAWING FIG. I shows a printing machineembodying a roller platen releasing device of the present invention.

FIG. 2 shows a sectional elevation of the carriage of the printingmachine taken along the line II II in FIG.

FIG. 3 shows a sectional view taken along the line I III in FIG. 2 andshows the roller platen in a printing position.

FIG. 4 shows the same sectional view as the view in FIG. 3, but showsthe roller platen in a non-printing retracted position.

FIG. 5 shows a sectional view taken along the line V V in FIG. 2.

FIG. 6 shows an exploded perspective view of a preferred embodiment ofthe present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Inreference to FIG. 1, aprinting bed 1 is at both ends thereof provided with a pair of endplates 10,10 which are each formed with an outwardly bent horizontalportion 16 at the top thereof and an inwardly bent horizontal portion 17as a foot at the lower part thereof. On the printing bed I, there areprovided a plurality of type wheels 18 for representing dates or salesaccounts. The type wheels have type characters formed on the peripherythereof and are arranged in a stack on the underside of the printingbed. Each type wheel has a part exposed above the printing bed Iprojecting from an opening I I formed in the printing bed. Around thetype wheels 18 on the printing bed I, there are provided positioningpieces 12,12 and 13,13 in a spaced relation. These positioning piecesare adapted to position a credit card and a material to be printed suchas a sales slip (not shown) in a predetermined position on the printingbed 1. Tipping actuating blocks 100,10011 are fixed on the printing bed,which are, as will be described later in detail, adapted to actuate areleasing lever for shifting the roller platen. A carriage 29 is mountedon the printing bed 1 for transverse movement in a printing stroke and areturn stroke between the end plates 10,10.

In reference to FIGS. 2 and 6, the device of the present invention isaccommodated in the carriage 29 and comprises mainly a main frame 21, asupporting frame 3, a swingable roller platen frame 4 on an eccentricshaft 5, a supporting plate 6, a connecting plate 7, a releasing lever9, a holding lever 60 and a roller platen 8. The carriage 29 has a cover28 of U-shape in the cross section to cover the U-shaped main frame 2 Onthe depending walls at both ends of the main frame 2, wheel rollers 23and 24 are rotatably mounted .by means of shafts 25 and 26 respectively.As :shown in FIG. 2, the rollers 23 are in engagement with the upperfaces along the edges of the printing bed I while the rollers 24 are inengagement with the lower faces along the edges of the printing bed sothat the carriage 29 may be moved on the printing bed transverselythereof.

The supporting U-shape frame 3 is fixedly attached to the main carriageframe 2 by means of fastening screws 22,22 with washers 21,21 beinginserted between the screws and the upper transverse wall of the mainframe 2 and placed in the depressions 20,20 in the transverse wall. Theeccentric shaft 5 is fixedly supported on the supporting frame 3 betweenthe depending leg walls thereof. The reduced portion 51 of the eccenricshaft is eccentric to the central axis of the shaft and fitted into abearing hole in the depending wall 34 of the supporting frame 3 whilethe reduced portion 52 is concentric with the central axis of the shaft5 but fitted into an eccentric ring 31 which is in turn fixedly fittedin the boss on the opposite depending wall of the supporting frame 3 bymeans of a screw 32.

The roller platen frame 4 is swingably supported within the supportingframe 3 on the eccentric shaft 5 which passes through the aligned holes47,48 respectively formed in the upper parts of the depending walls ofthe swingable frame 4. The roller platen 8, which is made of plastic orother known material, is rotatably supported by frame 4 on a transverseshaft which is at both ends thereof fitted into the aligned holes formedin the lower part of the oppositely depending walls of the swingableframe 4. However. in the embodiment shown in FIG. 6, one end of theroller platen 8 is supported by a support shaft 46 which is fitted intothe axial bore of the roller platen 8. The support shaft 46 is supportedon a support piece 44 adjustably mounted by means ofa screw on onedepending wall of the swingable frame 4.

The angular movement of frame 4 in one direction is restricted by avertical wall 2 provided between the opposite depending walls ofthe mainframe 2, on which abut the projections 4',4' respectively formed at thelower ends of the opposite depending walls of frame 4 when the swingableframe 4 is swung on one direction around the eccentric shaft 5 to aprinting position in which the central axis of the roller platen 8 is,as shown in H6. 3, located at a point in the one direction just passedover the vertical plane Y Y from the axis of the shaft 5 to the printingbed 1. The swinging movement of frame 4 in the opposite direction to aretracted inoperative position is restricted by a recessed portion 33provided on one depending wall of the supporting frame 3, which isengaged by the extension of the roller platen shaft 40 or the supportingshaft 46 on one side ofthe depending wall of frame 4 when frame 4 isswung in the opposite direction around the eccentric shaft 5. It is tobe noted that the displacement angle of the swingable frame 4-in theopposite direction around the eccentric shaft 5 is larger than thedisplacement angle in the one direction in relation to the plane Y-Yfrom FIGS. 3 and 4.

The eccentric shaft 5 is prevented from axially shifting by theeccentric ring 31 which is at one end thereof in contact with thestepped shoulder of the eccentric shaft 5 and also by of a collar 41which is fixedly secured on the opposite end portion of the eccentricshaft 5 by screw 42 and is in contact with the inner face of theoppositedepending wall of the swingable frame 4.

For the purpose of holding the roller platen 8 in arrested restrictedpositions, a holding plate 6 is at the upper part thereof mounted on theextension of the reduced portion 51 of the eccentric shaft 5 at one endof the supporting shaft 3, and a holding lever is turnably mounted onthe lower end part of the holding plate 6 by means of a pin 61. A spring62 is at one end hooked into a notch 64 at the top edge of the holdingplate 6 and is at the other end anchored in the holding lever 60 to biasthe holding lever in upward, see FIG. 5. The holding lever 60 is at theupper surface thereof provided with a depressed engaging face 60 at theintermediate partthereof and has a sloped depressed engaging face 63 atthe free end part thereof. The engaging faces 60,63 of the holding lever60 are adapted to be in engagement with the free follower part 43a of anarresting pin 43 which also turnably supports the releasing lever 9 onthe lower part of one depending wall of roller platen frame 4.

The releasing lever 9 is at the top thereof provided with an inclinedcontacting surface or edge 90 and has a lower arm portion 91 which isadapted to engage the fixed actuating blocks 100,100a on the printingbed 1 as shown in FlGS. 3, 4 and 5 during the transverse movement of thecarriage 29 over the printing bed 1. At the upper part of one dependingwall of the swingable frame 4, the connecting contact plate 7 isturnably mounted on the reduced portion 51 of the eccentric shaft 5. Theplate 7 is provided with an inclined contact face 72 at the lower endthereof. Spring is at one end hooked into a hole 71 at the top part ofthe plate 7 and is at the other end anchored to a hole 4" in the lowerpart of the one depending wall of the swingable frame 4 to press theinclined contact edge 72 of plate 7 against the inclined contact face ofthe releasing lever 9. It is to be noted that the spring 70 is of aforce stronger than the force of the spring 62 acting on the holdinglever 60. The resilient connecting means 7, 70 connect the releasinglever 9 with the roller platen frame 4.

Therefore, the frame 4 can be swung by the shifting means 9, 91, 90, 72;7, 70 to the opposite restricted positions against the cam action ofholding lever 60 biased against follower projection 43a by spring 62,and is at the same time held arrested in the restricted positions by theaction of the same spring 62, due to the contact engagement between theholding lever 60 and the extension 43a of the pin 43 on the swingingframe 4.

The reduced portion 52 of the eccentric shaft 5 has a slot 53 for a toolat the free end thereof, and the free end of the reduced portion 52 islocated in alignment with openings 54 and 55 respectively provided inthe depending walls of the main frame 2 and of the cover 28. Therefore,the operator can insert an instrument such as a screw driver through theopenings 54in frame 2 and 55 in cover 28 and rotate the eccentric shaft5 to adjust the same relative to the swingable frame 4, thereby toadjust the position of the roller platen 8 with respect to the printingbed 1 for variably changing the pressure of the roller platen on thematerial to be printed. Such an adjustment of the roller platen 8 will,according to the present invention, give no adverse effects to thenormal cooperation between the releasing lever 9 and the fixed actuatingblocks 100,100a on the printing bed 1, because such a cooperation ismaintained by the tensioning action of spring 62.

- OPERATION After the type wheels 18 are manually rotated to select thetypecharacters for dates or sales accounts, and the credit card and thesales slip (not shown) are placed in the predetermined position on theprinting bed 1, the carriage 29 is transversely moved over the printingbed in a printing stroke in the direction as indicated by an arrow markA in FIG. 3 from the initial position as shown in HO. 1.

During the transverse movement of the carriage 29, the lower arm portion91 of the releasing lever 9 engages the block on the printing bed 1before the carriage arrives over the sales slip and turns the frame 4with the roller platen 8 in one direction around the eccentric shaft 5through the contact plate 7 and the spring 70 against the action ofspring 62, which causes resilient engagement between the holding lever61) and the extension 43a of the pin 43. The swinging movement of frame4 in this first direction is restricted by the vertical wall 2 of themain frame 2, which is contacted by the projections 4',4' providedrespectively on the lower ends of the opposite depending walls of theswingable frame 4, and the roller platen 8 is held in a printingposition closest to the printing bed 1 as shown in FIG. 3. The swingableframe 4 is held in an arrested restricted position, since the extension434 of the pin 43 is supported by the sloped depressed engaging face 63of the holding lever 60 which is biased on by spring 62.

As the carriage 29 is further moved in the same direction out of theposition shown in FIG. 5 the releasing lever 9 is now turned by block100 around the pin 43 against the action of the spring 70 and passesoverthe block 100, moving together with the carriage 29. The arm portion91 is forced by block 100 to rotate releasing lever 9 clockwise aboutpin 43a so that the contact face 90 presses against the contact face 72,particularly at point 90'. However, since point 72' of connecting lever7 is in this position located on the extension of a line connectingshaft portion 51 with the attaching point 71 of spring 70, theconnecting plate 7 is hardly rotated in counterclockwise direction whilethe releasing lever 9 turns clockwise to pass block 100. As the carriageis furthermoved, the roller platen 8 presses the sales slip (not shown)against the type characters on the printing bed 1 to print the same.During such a transverse movement of the carriage 29 in the printingdirection the lower arm portion 91 of the releasing lever 9 engagesanother tipping block 100a which is located at a position on theprinting bed 1 where the carriage 29 has passed over the sales slip andbeyond the end of the stack of type wheels 18. The releasing lever 9passes over the tipping block 100a in the same man ncr as it passes overthe first tipping block 100.

When the carriage 29 is now transversely moved in the return directionto the initial position as indicated by an arrow mark B in FIG. 4, thelower arm portion 91 of the releasing lever 9 engages the tipping block100a and turns the frame 4 in the opposite direction around theeccentric shaft 5 through the contact plate 7 and the spring 70, whilespring 62 causes contact engagement between the holding lever 60 and theextension 43a of the pin 43. The opposite swinging movement of the frame4 is restricted by the recessed portion 33 of the depending wall of thesupporting frame 3, which is to be contacted by the extension of theshaft 40 supporting the roller platen 8 or by the supporting shaft 46supporting the roller platen on one side thereof. The frame 4 isresiliently held in the inoperative retracted position of FIG. 4, sincetheextension 43a of the pin 43 is now supported by the depressedengaging face 60' of the holding lever 60 which is biased by spring 62.In the retracted position of the swingable frame 4, the roller platen 8is raised up from the printing position away from the printing bed 1.

During further returning movement of the carriage 29, the releasinglever 9 is now turned in the opposite direction around the pin 43against the action of spring 70 and gets over the tipping block 100a.The arm portion 91 is rotated so that face portion of edge 90 ofreleasing lever 9 presses against face portion 72" of contact face 72 ofconnecting contact plate 7, since in this position face portion 72" islocated far away from the extension of the line connecting point 71 withshaft portion 51, connecting plate 7 is rotated about shaft portion 51and the turning of members 7 and 9, with contact faces 90 and 72 slidingon each other, permits arm portion 91 to pass block 1110a during thereturn stroke of the carriage 29. As the carriage 29 is further moved inthe return direction, the retracted roller platen 8 will no more pressthe sales slip onto the printing bed 1. The releasing lever 9 91 passesblock in the same manner as block 1011a, and then the carriage 29returns to the initial position as shown in FIG. 3 completing theprinting cycle.

We claim:

1. A printing machine with a roller platen releasing device, comprisinga printing bed, type means mounted on said printing bed; carriage meansmounted on said printing bed for reciprocating movement over said typemeans in a printing stroke and in a return stroke; a roller platen framemounted on said carriage means for angular movement, and a roller platenhaving a follower projection and mounted on said frame for movementtherewith between a printing position cooperating with said type meansand a retracted position for bassing said type means by; holdingmeansfor arresting said roller platen frame and said roller platen insaid printing position during said printing stroke, and in saidretracted position during said return stroke; shifting means includingreleasing means turnably mounted on said frame and having a contactface, connecting means mounted on said carriage means and having another contact face slidingly abutting said contact face, and a springconnecting a portion of said connecting means with said frame; and twoactuating blocks secured to said printing bed on opposite sides of saidtype means and located in the path of movement of said releasing meansduring said strokes of said carriage means so that said releasing meansis turned in opposite directions during said printing and return strokesof said carriage means when engaging the respective actuating block, andcauses through said abutting contact faces and said connectingmeans'turning of said frame between said printing and retractedpositions, said holding means blocking said frame in said printing andretracted positions so that said slidingly abutting contact faces andsaid releasing means and connecting means moved relative to each otherwhen said releasing means passes over the respective actuating blockafter shifting said frame to one of the blocked positions thereof; saidholding means including a holding lever mounted on said carriage meansfor angular movement and having a cam face with a dwell separating twodepressed portions cooperating with said follower projection, andaspring biasing said holding lever toward said follower portion so thatshifting of said releasing means and of said frame places saidprojection in one of said depressed portions whereby said frame isyieldingly ar rested in said printing position and in said retractedposition, respectively.

2. Printing machine as claimed in claim 1, wherein said spring of saidresilient connecting means is stronger than said spring of said holdinglever so that said spring of said holding lever yields when saidreleasing means turns said frame between said printing and retractedpositions; wherein said follower projection is part of a pin; andwherein said releasing means is a lever mounted on said pin.

3. Printing machine as claimed in claim 1, wherein said spring of saidholding means is tensioned in a dead center position when said followerprojection engages said dwell so that said frame tends to assume one ofsaid positions thereof.

4. A printing machine with a roller platen releasing device, comprisinga printing bed, type means mounted on said printing bed; carriage meansmounted on said printing bed for reciprocating movement over said typemeans in a printing stroke and in a return stroke; a roller platen framehaving a follower projection and mounted on said carriage means forangular movement, and a roller platen mounted on said frame for movementtherewith between a printing position cooperating with said type meansand a retracted position for passing said type means by; resilientholding means for yieldingly arresting said roller platen frame and saidroller platen in said printing position during said printing stroke, andin said retracted position during said return stroke, shifting meansincluding releasing means mounted on said frame, and resilientconnecting means connecting said releasing means with said carriage sothat turning of said releasing means in opposite directions causesturning of said frame between said printing and retracted positions; andtwo actuating blocks secured to said printing bed on opposite sides ofsaid type means and located in the path of movement of said releasingmeans during said strokes of said carriage means so that said releasingmeans is turned in opposite directions during said printing and returnstrokes when engaging the respective leading actuating block and turnssaid roller platen frame between said printing and retracted positions;said holding means including a holding lever mounted on said carriagemeans for angular movement and having a cam face with a dwell separatingtwo depressed portions cooperating with said follower projection, and aspring biasing said holding lever toward said follower portion so thatshifting of said releasing means and of said frame places saidprojection in one of said depressed portions whereby said frame isyieldingly arrested in said printing position and in said retractedposition, respectively, said spring being tensioned in a dead centerposition when said follower projection engages said dwell so that saidframe is biased in a dead center position when said follower projectionengages said dwell so that said frame is biased to assume one of saidpositions.

5. A printing machine with a roller platen releasing device, comprisinga printing bed, type means mounted on said printing bed; carriage meansmounted on said printing bed for reciprocating movement over said typemeans in a printing stroke and in a return stroke; a roller platen framemounted on said carriage means for angular movement, and a roller platenmounted on said frame for movement therewith between a printing positioncooperating with said type means and a retracted position for passingsaid type means by; holding means for arresting said roller platen frameand said roller platen in said printing position during said printingstroke, and in said retracted position during said return stroke;shifting means including releasing means turnably mounted on said frameand having a contact face, connecting means mounted on said carriagemeans and having an other contact face slidingly abutting said contactface, and a spring connecting a portion of said connecting means withsaid frame; and two actuating blocks secured to said printing bed onopposite sides of said type means and located in the path of movement ofsaid releasing means during said strokes of said carriage means so thatsaid releasing means is turned in opposite directions during saidprinting and return strokes of said carriage means when engaging therespective actuating block, and causes through said abutting contactfaces and said connecting means turning of said frame between saidprinting and retracted positions, said holding means blocking said framein said printing and retracted positions so that said slidingly abuttingcontact faces and said releasing means and connecting means moverelative to each other when said releasing means passes over therespective actuating block after shifting said frame to one of theblocked positions thereof.

6. Printing machine as claimed in claim 5 wherein said releasing meansincludes a releasing lever having said contact face and an arm forengaging said actuating blocks, wherein said connecting means includes aconnecting lever having said other contact face, and wherein saidportion of said connecting lever is located remote from said othercontact face.

7. Printing machine as claimed in claim 5, wherein said carriage meansincludes an eccentric shaft means turnably supporting said roller platenframe, and in cluding an end portion projecting from said carriage andhaving means for engaging a tool so that said eccentric shaft means canbe manually turned for adjusting the distance between said roller platenon said roller platen frame and said type means in said printingposition.

8. Printing machine as claimed in claim 7, wherein said eccentric shaftmeans includes a main shaft portion, a first reduced end portion,eccentric to the axis of said main shaft portions and mounted in saidcarriage means, a second reduced end portion concentric to said axis,and being said projecting end portion and an eccentric ring for mountingsaid second reduced end portion on said carriage means.

9. Printing machine as claimed in claim 5, wherein said carriage meansincludes an abutment means; and wherein said roller platen frame abutssaid abutment means in said printing position.

1. A printing machine with a roller platen releasing device, comprisinga printing bed, type means mounted on said printing bed; carriage meansmounted on said printing bed for reciprocating movement over said typemeans in a printing stroke and in a return stroke; a roller platen framemounted on said carriage means for angular movement, and a roller platenhaving a follower projection and mounted on said frame for movementtherewith between a printing position cooperating with said type meansand a retracted position For bassing said type means by; holding meansfor arresting said roller platen frame and said roller platen in saidprinting position during said printing stroke, and in said retractedposition during said return stroke; shifting means including releasingmeans turnably mounted on said frame and having a contact face,connecting means mounted on said carriage means and having an othercontact face slidingly abutting said contact face, and a springconnecting a portion of said connecting means with said frame; and twoactuating blocks secured to said printing bed on opposite sides of saidtype means and located in the path of movement of said releasing meansduring said strokes of said carriage means so that said releasing meansis turned in opposite directions during said printing and return strokesof said carriage means when engaging the respective actuating block, andcauses through said abutting contact faces and said connecting meansturning of said frame between said printing and retracted positions,said holding means blocking said frame in said printing and retractedpositions so that said slidingly abutting contact faces and saidreleasing means and connecting means moved relative to each other whensaid releasing means passes over the respective actuating block aftershifting said frame to one of the blocked positions thereof; saidholding means including a holding lever mounted on said carriage meansfor angular movement and having a cam face with a dwell separating twodepressed portions cooperating with said follower projection, and aspring biasing said holding lever toward said follower portion so thatshifting of said releasing means and of said frame places saidprojection in one of said depressed portions whereby said frame isyieldingly arrested in said printing position and in said retractedposition, respectively.
 2. Printing machine as claimed in claim 1,wherein said spring of said resilient connecting means is stronger thansaid spring of said holding lever so that said spring of said holdinglever yields when said releasing means turns said frame between saidprinting and retracted positions; wherein said follower projection ispart of a pin; and wherein said releasing means is a lever mounted onsaid pin.
 3. Printing machine as claimed in claim 1, wherein said springof said holding means is tensioned in a dead center position when saidfollower projection engages said dwell so that said frame tends toassume one of said positions thereof.
 4. A printing machine with aroller platen releasing device, comprising a printing bed, type meansmounted on said printing bed; carriage means mounted on said printingbed for reciprocating movement over said type means in a printing strokeand in a return stroke; a roller platen frame having a followerprojection and mounted on said carriage means for angular movement, anda roller platen mounted on said frame for movement therewith between aprinting position cooperating with said type means and a retractedposition for passing said type means by; resilient holding means foryieldingly arresting said roller platen frame and said roller platen insaid printing position during said printing stroke, and in saidretracted position during said return stroke, shifting means includingreleasing means mounted on said frame, and resilient connecting meansconnecting said releasing means with said carriage so that turning ofsaid releasing means in opposite directions causes turning of said framebetween said printing and retracted positions; and two actuating blockssecured to said printing bed on opposite sides of said type means andlocated in the path of movement of said releasing means during saidstrokes of said carriage means so that said releasing means is turned inopposite directions during said printing and return strokes whenengaging the respective leading actuating block and turns said rollerplaten frame between said printing and retracted positions; said holdingmeans including a holding lever moUnted on said carriage means forangular movement and having a cam face with a dwell separating twodepressed portions cooperating with said follower projection, and aspring biasing said holding lever toward said follower portion so thatshifting of said releasing means and of said frame places saidprojection in one of said depressed portions whereby said frame isyieldingly arrested in said printing position and in said retractedposition, respectively, said spring being tensioned in a dead centerposition when said follower projection engages said dwell so that saidframe is biased in a dead center position when said follower projectionengages said dwell so that said frame is biased to assume one of saidpositions.
 5. A printing machine with a roller platen releasing device,comprising a printing bed, type means mounted on said printing bed;carriage means mounted on said printing bed for reciprocating movementover said type means in a printing stroke and in a return stroke; aroller platen frame mounted on said carriage means for angular movement,and a roller platen mounted on said frame for movement therewith betweena printing position cooperating with said type means and a retractedposition for passing said type means by; holding means for arrestingsaid roller platen frame and said roller platen in said printingposition during said printing stroke, and in said retracted positionduring said return stroke; shifting means including releasing meansturnably mounted on said frame and having a contact face, connectingmeans mounted on said carriage means and having an other contact faceslidingly abutting said contact face, and a spring connecting a portionof said connecting means with said frame; and two actuating blockssecured to said printing bed on opposite sides of said type means andlocated in the path of movement of said releasing means during saidstrokes of said carriage means so that said releasing means is turned inopposite directions during said printing and return strokes of saidcarriage means when engaging the respective actuating block, and causesthrough said abutting contact faces and said connecting means turning ofsaid frame between said printing and retracted positions, said holdingmeans blocking said frame in said printing and retracted positions sothat said slidingly abutting contact faces and said releasing means andconnecting means move relative to each other when said releasing meanspasses over the respective actuating block after shifting said frame toone of the blocked positions thereof.
 6. Printing machine as claimed inclaim 5 wherein said releasing means includes a releasing lever havingsaid contact face and an arm for engaging said actuating blocks, whereinsaid connecting means includes a connecting lever having said othercontact face, and wherein said portion of said connecting lever islocated remote from said other contact face.
 7. Printing machine asclaimed in claim 5, wherein said carriage means includes an eccentricshaft means turnably supporting said roller platen frame, and includingan end portion projecting from said carriage and having means forengaging a tool so that said eccentric shaft means can be manuallyturned for adjusting the distance between said roller platen on saidroller platen frame and said type means in said printing position. 8.Printing machine as claimed in claim 7, wherein said eccentric shaftmeans includes a main shaft portion, a first reduced end portion,eccentric to the axis of said main shaft portions and mounted in saidcarriage means, a second reduced end portion concentric to said axis,and being said projecting end portion and an eccentric ring for mountingsaid second reduced end portion on said carriage means.
 9. Printingmachine as claimed in claim 5, wherein said carriage means includes anabutment means; and wherein said roller platen frame abuts said abutmentmeans in said printing position.